Master cylinder construction affording automatic re-phasing of master and slave cylinders



Oct. 17, 1967 R E 3,347,043

. MASTER CYLINDER CONSTRUCTION AFFORDING AUTOMATIC RE-PHASING OF MASTERAND SLAVE CYLINDERS Filed NOV. 22, 1965 2 Sheets-Sheet l I9 34 29 33 35I3 :5 l6 I7 EVANS GLENN FREESE INVENTOR.

ATTORNEY Oct. 17, 1967 ca. FREESE 3,347,043

E. MASTER CYLINDER CONSTRUCTION AFFORDING AUTOMATIC RE-PHASING OF MASTERAND SLAVE CYLINDERS Filed Nov. 22, 1965 2 Sheets-Sheet 2 22 EVANS GLENNFREESE INVENTOR.

ATTORNEY United States Patent Ofitice 3,34i7fl4 3 Patented Get. 17, 19673,347,043 MASTER CYLINDER CONSTRUCTION AFFORD- ING AUTOMATIC RE-PHASINGF MASTER AND SLAVE CYLINDERS Evans Glenn Freese, Hutchinson, Kans.,assignor to The Cessna Aircraft Company, Wichita, KHIXS., a corporationof Kansas Filed Nov. 22, 1965, Ser. No. tl9,113 6 Claims. (Cl. 60-545)This invention relates to a unique construction for a master hydrauliccylinder of the type capable of performing useful work whilesimultaneously controlling the coordinated operation of associated slavecylinders, which also perform useful work. The cylinder construction isalso capable of use in a hydraulic system in which it per forms its workindependent of any slave cylinder association or operation.

A master cylinder construction embodying my inven tion is illustratedand described herein associated with a single slave cylinder. In such acombination, where both master and slave cylinders are simultaneouslyperforming useful work at widely separated locations, it is oftenrequired that the pistons and rods of the two cylinders start theirmovement simultaneously, travel at substantially the same velocity,travel the same distance, and reach the ends of their respective strokesat substantially the same time. This is true, for instance, when twosuch cylinders are connected to raise and lower the respective oppositeends of the reel on a combine or other harvester. Such coordinatedaction of the cylinders is required in order to maintain the elongatedreel in a level position throughout the raising and lowering operation.

The difliculty of maintaining such coordinated action over an extendedperiod of weeks is primarily due to uneven wear of the working parts ofthe two working cylinders, particularly the hydraulic fluid seals. Sealwear causes leakage, and due to this leakage the piston and rod of onecylinder may not complete its travel to the full end of its permittedstroke in either direction, resulting in a progressive shortening of thelength of its stroke. In other words the pistons and rods of the twocylinders get out of phase.

It is a primary object of my invention to provide a master cylinderconstruction which automatically rephases the piston positions of themaster cylinder and the associated slave cylinder or cylinders at eachend of their respective strokes, regardless of the relative degree ofwear on the working parts of the respective associated cylinders over anextended period. By so re-phasing the positions of the respectivepistons at each end of their respective strokes, assurance is providedthat all pistons begin their return strokes simultaneously, and that allpistons travel to the full ends of their respective permitted strokes ineach direction.

Another important object of the invention is to provide a mastercylinder construction which automatically provides a relief against overpressurization of one cylinder due to the fact that the piston of thatcylinder reaches the end of its permitted stroke prior to the time thepiston of an associated cylinder reaches the end of its permittedstroke.

Another object is to provide a master cylinder construction whichaccomplishes the above described results without the use of poppetvalves, manual valves, etc., which are commonly used to accomplishre-phasing of associated working cylinders, whether they are connectedin series or in parallel.

An additional object of the invention is to provide a double actingworking cylinder construction which provides relief against internalover pressurization of the cylinder at both ends of the piston stroke incase the control valve directing pressure fluid to either end of thecylinder is not closed just prior to or at approximately the instant thepiston reaches the end of its stroke in either direction.

The invention will be more clearly understood when the followingdescription is read in connection with the accompanying drawings, inwhich:

FIG. 1 is a central longitudinal sectional view through a hydraulicworking cylinder embodying my invention, shown connected in series to anassociated hydraulic slave cylinder, the hydraulic system for actuatingboth cylinders being shown schematically, the respective pistons androds of both cylinders being shown at the inner ends of their permittedstrokes;

FIG. 2 is a view similar to FIG. 1, with the respective pistons and rodsof both cylinders being shown at the outer ends of their permittedstrokes; and

FIG. 3 is a fragmentary view of a portion of the cylinder shown in thelower part of FIG. 2, and includes optional check valves which are notincluded in the other drawing figures, yet which constitute a part of myinvention.

A cylinder construction which embodies my invention is shown in thelower portion of FIG. 1, and is designated as a whole by the numeral 10.For clarity in description cylinder 10 is shown connected in series to aslave cylinder 11 by means-of a conduit 12. Cylinder 10 will be referredto herein as a master cylinder, although it should be understood thatthis cylinder may be used in any hydraulic system as a double actingworking cylinder, completely disassociated from any slave cylinder.

C0nstructi0nFIGS. J and 2 Referring to FIG. 1, master cylinder 10includes a barrel 13 having a fixed head 14 at one of its ends and aremovable piston rod bearing 15 at its other end. Bearing 15 carriesseals 16 and 17. The head 14 and the inner end 18 of bearing 15 serve astravel limit stops for a piston 19.

Barrel 13 is provided with relatively large longitudinally spaced ports20 and 21, and a pair of respectively associated fluid escape orifices22 and 23. Port 20 and orifice 22 both communicate with a conduitattachment fitting 24, while port 21 and orifice 23 both communicatewith a similar conduit fitting 25.

Piston 19 carries an integral stop 26, and is connected to areciprocable rod 27. Piston 19 is provided with a central annular groove28 which seats an annular wall seal 29, adjacent annular lands 30 and 31which are of a diameter to fit the barrel wall snugly, grooves 32 and33, and outside lands 34 and 35. Piston 19, of course, divides theinterior of barrel 13 into two pressure fluid chambers 36 and 37.

The length of permitted travel of piston 19 between stops 14 and 18, andthe relative locations of ports 20 and 21 and orifices 22 and 23 withrespect to the location of seal 29 on the piston are such that whenpiston 19 is at the inner end of its stroke, as in FIG. 1, port 20 islocated between seal 29 and head 14 and openly communicates with chamber36. With the piston in this position orifice 22 is located between seal29 and chamber 37, and if the fluid pressure in chamber 37 is greaterthan the pressure in chamber 36 and fitting 24, fluid from chamber 37may leak past land 35 and escape through orifice 22 into fitting 24. Anyflow of fluid through escape orifice 22 in the opposite directon due toa higher pressure in fitting 24- than in chamber 37, is incidental andimmaterial in the illustrated series hook-up of master and slavecylinder, because the least outward movement of piston 19 causes seal 29to pass orifice 22, thus cutting off the fluid escape route into chamber37.

In the same manner, when piston 19 is located at the outer end of itspermitted stroke, as in FIG. 2, port 21 is located outside seal 29 andopenly communicates with chamber 37. At the same time escape orifice 23is located inside seal 29. If fluid pressure in chamber 36 is higherthan in fitting 25 and chamber 37, fluid can leak past land 34, throughorifice 23 and into fitting 25. Leakage of fluid through orifice 23 inthe opposite direction, due to the existence of a higher pressure infitting 25 than in chamber 36, is inconsequential.

In the hydraulic system illustrated, master cylinder fitting 25 isconnected by conduit 12 to a port 38 in a wall of single acting slavecylinder 11. Port 33 communicates with a pressure chamber 39, withinwhich a combination piston and rod is reciprocableThe chambers 37 and 39have equal volume capacities, regardless of the permitted length ofstroke of the piston rods 27 and 40. A piston rod seal 41 normallypreventsleakage from slave cylinder chamber 39 as the rod reciprocates.A snap ring 42 is seated in an annular groove near the inner end of rod40, and serves as a stop to limit outward movement of the rod in itscylinder. Inward movement of rod 40 is limited by contact of the innerend of the rod with an inwardly projecting abutment 43, integral withthe cylinder end wall.

Operation With both pistons 27 and 40 positioned at the inner ends oftheir respective strokes, as in FIG. 1, and with the chambers 36, 37 and39, and conduits 12 and 44 completely filled, fluid under pressure isdelivered from a pump 45 or other source, through conduit 44 and port 20into master cylinder chamber 36, when a control valve 46 is properlyadjusted. Theinstant piston 19 starts to move outward, fluid is forcedfrom chamber 37 through conduit 12 and into slave chamber 39, and piston40 simultaneously starts to move outward. It will be assumed that bothpiston rods are operating against load forces applied in the directionsindicated by the arrows 47 and 48.

Case No. 1Exzension Assuming that there is fluid leakage from slave chamber 39 past seal 41 due to a worn seal or because of a greater load onpiston rod 40, rod 40 would normally stop traveling before reaching theouter end of its stroke, while master piston 19 would continue to travelto the full end of its stroke. This could occur because of insuflicientfluid in master chamber 37 to completely fill slave chamber 39 afterfluid had leaked from that chamber (FIG. 2).

Under this condition supplemental fluid under pressure from source 45would leak past land 34 (FIG. 2), through orifice 23, through conduit 12and into slave chamber 39, thus forcing piston 40 to the full outer endof its stroke, regardlessof leakage from chamber 39. The pistons androds of both master and slave cylinders are thus re-phased at the outerends, of their respective strokes, each time the movement cycle isrepeated.

Case No. 2Retracti0n With both pistons at the outer ends of theirrespective strokes, as in FIG. 2, control valve 46 can be adjusted toits FIG. 2 condition, which connects master chamber 36 to a systemreservoir 49, and allows both pistons to simultaneously start theirinward travel under the influence of their respective loads.

If master piston 19 reaches the full end of its permitted inward travelbefore slave piston 40 does, excess fluid can pass from chamber 39(FIG. 1) through chamber 37, past land 35, and through escape orifice 22into conduit 44 and to the reservoir, thus permitting piston 40:totravel to the full inner end of its stroke.

If slave cylinder piston 40 reaches the inner end of its stroke beforemaster piston 19 has completed its stroke, and a void is created inchamber 37 as piston 19 continues to the end of its stroke, that void isfilled through escape orifice 22 by pressure fluid from the pump beforeeither piston again starts its outward travel during the next cycle. Thepistons and rods of the two cylinders are thus re-phased at each of theends of their respective strokes.

FIG. 3 Construction 0perationFl G. 3

The washer type check valves 50 and 51 are useful in reventing unevenextension or retraction of the two piston rods 27 and 40 in case .rod 27is loaded much more heavily than rod 40.

Under such a condition, with both pistons at the inner ends of theirrespective strokes as in FIG. 1, check valve 50 prevents pressure fluidfrom traveling through escape orifice 22, chamber 37, and to slavechamber 39, and moving pistonv 40 outward while master piston 27 remainsstationary under its heavier load.

Withboth pistons at the outer ends of their respective strokes, withpiston rod 49 loaded much higher than master rod 27, and with controlvalve 46 open only slightly to provide slow inward movement of thepistons, checkv valve 51 prevents fluid from being forced from slavecylinder chamber 39 through escape orifice 23 and conduit 44 toreservoir. Rod 40 is thus prevented from moving inward in its cylinderunder its greater load, while the pressure build upin master chamber 36temporarily prevents rod 27 from moving inward under its lighter load.Uneven retraction or extension of the unequally loaded piston rods isthus prevented.

It will be understood from the above description of the master cylinderconstruction that a number of master cylinders could be connected inseries, and that the first master would extend and retract the pistonsof all the cylinders in unison. By varying cylinder capacities the therate and extent of rod movement in the various cylinders can also bevaried to meet requirements. It will also be understood that the fluidescape orifices 22 and 23 in each mastercylinder of the series wouldaccomplish rephasing of all pistons at each end of their respectivestrokes.

Having described the invention with suflicient clarity to enable thosefamiliar with this art to construct and use it, I claim:

1. A hydraulic actuator assembly comprising:

an elongated cylinder;

a piston having limited reciprocable movement within the cylinder, anddividing the cylinder into first and second chambers;

a first port through a wall of the cylinder affording open exteriorfluid communication with said first chamber regardless of pistonposition in the cylinder;

a first fluid escape orifice through a wall of the cylinder located toafford restricted exterior communication with the second chamber onlywhen the piston is at one end of its permitted stroke;

a second port through a wall of the cylinder affording open exteriorcommunication with said second chamber regardless of piston position inthe cylinder; and

a second fluid escape orifice through a wall of the cylinder located toafford restricted exterior communication with the first chamber onlywhen the piston is at the other end of its permitted stroke.

2. The actuator described in claim 1, and:

fluid conducting means affording communication exterior of the cylinderbetween each of said ports and the respectively adjacent fluid, escapeorifice.

3. The actuator described in claim 1, and:

a check valve for each of said escape orifices affording flow of fluidoutward only through the respective orifices.

4. In a hydraulic actuator which includes an elongated cylinder and apiston having limited reciprocatory move ment therein, and which dividesthe cylinder into first and second chambers, said cylinder includingseparate means for conducting fluid into and from the respectivechambers, the improvement in such an actuator which Comprises:

a first fluid escape orifice through a Wall of the cylinder located toaflord restricted egress of fluid from said second chamber when thepiston has moved to a position to reduce the first chamber to minimumvolume capacity; and

a second fluid escape orifice through a wall of the cylinder located toaflord restricted egress of fluid from said first chamber when thepiston has moved to a position to reduce said second chamber to minimumvolume capacity.

5. The actuator described in claim 4, and:

a check valve for each of said escape orifices affording flow of fluidoutward only through the respective orifices.

6. A hydraulic actuator assembly comprising:

an elongated cylinder;

first and second longitudinally spaced fluid inlet and outlet fittingsin the cylinder wall;

first and second longitudinally spaced fluid inlet and outlet portsthrough the cylinder wall communicating respectively with the first andsecond inlet and outlet fittings;

first and second longitudinally spaced fluid escape orifices through thecylinder wall communicating respectively with the first and second inletand outlet fittings, one orifice adjacent each of said ports, thelongitudinal spacing between the orifices being less than thelongitudinal spacing between said ports, and the fittings, ports andorifices being in substantial longitudinal alignment along the cylinderwall;

a piston having limited reciprocable movement in the cylinder; and

an annular seal or packing carried by the piston for sealing between thepiston and the internal wall of the cylinder, and for thus dividing thecylinder into first and second fluid pressure chambers,

the location of the piston at each end of its permitted stroke and thespacing between and location of the ports and the orifices being sorelated, each to the other, that:

(a) when the piston is at one end of its stroke the piston seal islocated between the first port and the adjacent first orifice, the firstcylinder chamber is in open communication with the first fitting throughthe first port, and the second cylinder chamber is in restrictedcommunication with the first fitting through said first orifice; and

(b) when the piston is at the other end of its permitted stroke thepiston seal is located between the second port and the adjacent secondorifice, the second cylinder chamber is in open communication with thesecond fitting through the second port, and the first cylinder chamberis in restricted communication With the second fitting through thesecond orifice.

References Cited UNITED STATES PATENTS 2,312,337 3/1943 Hughes -545 X2,539,720 l/1951 Bender 6054.6 2,591,793 4/1952 Dubois et al. 60-54.52,766,590 10/1956 Erwin et al. 6054.5 2,882,685 4/1959 Carlsen et al.60-545 2,997,849 8/1961 Shimanckas 6054.5

MARTIN P. SCHWADRON, Primary Examiner. R. R. BUNEVICH, AssistantExaminer.

1. A HYDRAULIC ACTUATOR ASSEMBLY COMPRISING: AN ELONGATED CYLINDER; APISTON HAVING LIMITED RECIPROCABLE MOVEMENT WITHIN THE CYLINDER, ANDDIVIDING THE CYLINDER INTO FIRST AND SECOND CHAMBERS; A FIRST PORTTHROUGH A WALL OF THE CYLINDER AFFORDING OPEN EXTERIOR FLUIDCOMMUNICATION WITH SAID FIRST CHAMBER REGARDLESS OF PISTON POSITION INTHE CYLINDER; A FIRST FLUID ESCAPE ORIFICE THROUGH A WALL OF THECYLINDER LOCATED TO AFFORD RESTRICTED EXTERIOR COMMUNICATION WITH THESECOND CHAMBER ONLY WHEN THE PISTON IS AT ONE END OF ITS PERMITTEDSTROKE; A SECOND PORT THROUGH A WALL OF THE CYLINDER AFFORDING OPENEXTERIOR COMMUNICATION WITH SAID SECOND CHAMBER REGARDLESS OF PISTONPOSITION IN THE CYLINDER; AND A SECOND FLUID ESCAPE ORIFICE THROUGH AWALL OF THE CYLINDER LOCATED TO AFFORD RESTRICTED EXTERIOR COMMUNICATIONWITH THE FIRST CHAMBER ONLY WHEN THE PISTON IS AT THE OTHER END OF ITSPERMITTED STROKE.